1. Field of the Invention
The invention relates to uniformly spreading continuous multiple filament fiber bundles and unidirectionally arranging in parallel for the continuous production of prepregs having reduced gaps and improved fiber-resin distribution. More specifically, the invention relates to apparatus using tension control throughout the apparatus and higher differential speeds between the surface periphery of driven rollers and the line speed (or running speed) of the fiber bundle, and methods for using same to achieve prepreg material used for fabricating articles of fiber-reinforced plastics that has a uniform thickness and few defects in appearance.
2. Description of the Related Art
Prepregs, in which reinforcing fibers are impregnated with a matrix resin, are well known in the art and are broadly used in various industrial/high performance fields, such as for aircraft and automobile materials, medical materials, and formed materials for sports and leisure (e.g., fishing rods, golf club shafts, badminton rackets, tennis rackets, etc.).
Producing more uniform prepregs with less thickness irregularity is preferable and critical to overall product quality. In order to achieve this, it is necessary to open (i.e., spread) the reinforcing fiber bundle before impregnating it with a matrix resin when forming a prepreg, for reducing the thickness of the reinforcing fiber bundle and for letting the matrix resin sufficiently fill the clearances between the single fibers of the reinforcing fiber bundle.
Accordingly, the technique for efficiently and properly opening or spreading the raw reinforcing fiber bundles is critical for producing a prepreg having uniform thickness, reduced gaps between fibers, and proper fiber-resin distribution. Various apparatus and methods for spreading fiber bundles and/or making pre-pregs are known in the art and include, for example, those described in U.S. Pat. Nos. 4,495,017; 5,042,122; 5,182,839; and 6,743,392.
Additionally, it is generally known that tension is the prime mover for spreading fiber bundles containing multiple filaments. Thus, higher tension typically creates wider spread of the fibers in the bundle. However, too high a tension makes impregnation difficult due to decreased permeability of the fiber in relation to the resin, roping of the fibers, and damaging the fibers (thereby causing fuzz) or breaking the fiber. Increased tension also increases forces and torques throughout the apparatus which leads to increased process costs.
Accordingly, the apparatus and methods for spreading multiply adjacent fiber bundles having multiple filaments for the continuous production of prepreg require further improvement. Apparatus and methods that uniformly spread continuous multiple filament fiber bundles and unidirectionally arrange the spread fibers in parallel for the continuous production of prepregs having reduced gaps and improved fiber-resin distribution would be a useful advance in the art and could find rapid acceptance in the industry.